This page has information on my GM-10 Geiger Counter. I use this to check on background radiation. Sometimes when someone has had radiation treatments the can check with me to see how much they are glowing.

Here is a link to near real time background radiation in Pine Bush, NY 

http://rad.onesty.com/pbdata.png

This link is to a map of other GM-10 users in the USA

http://www.blackcatsystems.com/RadMap/map.html